Intermittent Servo Problem - When Wet!

[Shabazmo]

This problem has happened twice in 2 years. There is a loss of braking ability and the pedal becomes very hard and only depresses a small amount. On both occasions my wife was driving the Galaxy and it was frightening due to the time it took to stop, such that she had to swerve to avoid hitting a vehicle. This tells me that the servo is not working. However when moving off, the problem disappears. What makes the problem interesting is that both problems occurred when the roads were very wet. Now i know you will say "wet brakes" but we both have driven the Galaxy lots when its been wet and never experienced such a problem.

 

So servo fails when wet - Any ideas?

[gregers]

do you still have your undertray fitted?

[Shabazmo]

Tray still fitted but not sure what could cause the problem if it was not fitted

[chrispb123456]

Check vacuum pipe connections at servo and vacuum pump

[daddyfixit]

wet weather shouldnt affect brakes, but as already suggested check the pipework from the servo to the vacuum pump on the engine carefully. if its a loose fit at either end or it is cracked/split, then it will leak and prevent servo from helping you stop the car.

[alan_131]

I think for the servo to work, you need two things - vacuum before you apply the brakes - and access to air at atmospheric pressure when you apply them. On old-fashioned servos - and it might still be the same for some - there was a small felt filter mounted on the servo which, if it became obstructed, limited the air in when you braked - and hence the servo effect was very limited. Just wondering if, if your vacuum supply is ok, check valves working, etc etc, if the point where the air gets into the servo when you brake was getting wet, it might block air in - a bit like breathing through a wet cloth... It's a real stretch, but it's the only thing I can think of that being wet might affect.

Good luck with finding the problem - this intermittent stuff is a real pig...

[Shabazmo]

Thanks for your ideas and Alan, your logic sounds interesting. I am convinced that torrential rain has caused the problem so I will examine every part of the servo and report back

[Shabazmo]

I found a fault. I removed the vacuum pipe from the pump and the servo and found that iy joins in the misddle with a one way valve. The pipe from the servo to the one way valve was split where it joined onto the valve. What must have happened is that the engine must have moved forward to create a larger gap in the split and reduce the servo vacuum to zero. Why it has only happened twice in 2 years and only in torrential rain, I don't know. What's annoying is that the part is

[Shabazmo]

I decided not to spend